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forestry-final-1

Terms

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anizotropic
=wood exhibits different physical properties (strength, shrinking, swelling, compression) when tested along 3 tree directional axes
properties characteristic of certain species only
variation between woods in:
a. specific gravity
b. hardness
c. strength properties
d. mashining
e. gluing
f. durability
g. reaction to chemicals
which factors determine the properties of wood?
a. growth
b. structure
c. composition of the material
3 surfaces of wood
a. transverse (cross-sectional) surface is used the most
b. tangential surface
c. radial surface
cross section of a wood fiber (inside to out)
a. lumen
b. secondary wall
c. primary wall
d. middle lamella
what is the distribution of content of wood
cellulose (40-50%)
hemicellulose (20-30%)
lignin (15-30%)
properties common to all woods
a. all tree stems have a predominately vertical arrangement of cells
b. all wood is cellular in structure
c. all wood contains cellulose, hemicellulose, and lignin
d. all wood is anizotropic
e. all wood is hygroscopic
what is the result of moisture variations?
- it produces dimensional changes which are due to its anisotropic nature, unequal in the n= three tree directions
why is it relevant to distinguish between certain species?
-must have positive identification as a basis for its manufacturing, marketing, and proper use
3 tree directional axes
a. radial
b. tangential
c. longitudinal
why is understanding the properties of wood important?
-to utilize the wood correctly
which wood fibers are on average longer, softwoods (coniferous) or hardwoods (deciduous)
softwoods (coniferous)
variablity within a species
a. variablity from tree to tree
b. variability in wood taken from different places
c. variability within a given piece of wood (early or late wood)
what are the fundamental studies of wood
a. properties that are common to all woods
b. properties that are characteristic only to certain species
c. degree of variability of properties that may be present within a species
hygroscopic
=wood loses and gains moisture as a result of changes in the atmospheric humidity and temperature

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